I would only throw into the mix, clearly understand your own listening room before listening to any speakers. I know my room, I know how I have to lay out my tunes for best results. I know that very small, very low sensitivity speakers won't do well in my room. I know that I have very good room boundries to produce bass and don't have too many nasty room nodes to deal with. Figure out what hard and soft surfaces do to the mid and high frequencies in your room. You can then have your information as a reference as you compare your listening environment where ever you are and have a better chance to get the results that you are after at home. Like some of the others, I would strongly recommend a good used pair. If they aren't what you like, easier to move without getting bitten too hard. Good Luck, Tim |
Methodology????? A great thread on its own... My first impressions are based on tonal balance, is the bass tight, fast, full, boomy??? Is the mid range through the top end articulate, detailed and smooth? I've built alot of speakers in my time, I'm a stickler for drivers matching sensitivity and am annoyed by mis matches. Next, I listen for sound stage, I have recordings that I am very aware of. Is the stage as deep, wide, tall as I am used to, how is instrument placement on stage? Are these speakers dynamic? Yes/No, what amplification are they using and how does that affect the dynamics, warmth or lack of, dryness or sweetness on top or total accuracy. You get the idea, this can go on and on front end? cd? phono section, cables, yadda yadda yadda. Good luck, Tim |
Speaker typically lean toward having a inductive load or capacitive load, these are normally called phase angles, they are measured in degrees. Phasing that tends toward the plus side(inductive) are tube friendly, speakers that lean toward the negative side (capacitive) are not. This is the more important factor, most tube amps will handle a 4 ohm load just fine with an inductive load. And many will handle an 8 ohm load that leads capacitive ok, but hard capacitive spikes are hard on tubes,even on an 8 ohm load and not tolerated on a 4 ohm load. Many impedance charts also include phasing on those charts. On one side of the chart you will see numbers that indicate impedance 2-4-8-12-16 etc. The other side will have a 0, then degrees going
up (inductive) and degrees going down (capacitive). If using tubes, it is almost imperative to get phasing charts on a speaker. I hope this helps, Tim |
Sensitivity won't matter, if you have inductive speakers and enough power to get to the listening levels that you require. I looked up the Mac MC275, it is 75 watts, you should be fine with a minimum of 86db sensitivity. That will give you 101db output @ 32 watts. Not rock concert levels, but certainly live Jazz venue volume levels. |
Hi Honest1,
Agreed, I understand where you are coming from. I don't understand the argument. Sensitivity is rated @ 1 watt 1 meter regardless of a speakers impedance, as everyone has discussed above. It takes varying degrees of voltage to derive the power rating of 1 watt depending on the resistance of the speaker. It is the voltage that changes to measure 1 watt. The power rating of 1 watt is what we measure sensitivity. Varying degrees of voltage change the efficiency. I've had my head on backwards more than once. Either way, I have talked with Ralph and appreciate him, I have no doubt that we both understand the concept. Good Listening, Tim |
Hi Atmasphere, I think we are on the same page here. I have built 1 amp and modded a few, but I'm a simple minded speaker guy. I try to speak in the simplest terms possible on these forums, because it took my feeble mind a long time to get where I am, which is mediocre.
Sensitivity is a measurement of power, so 1 watt input measured @ 1 meter gives an spl or sensitivity rating... so yes 2.83 volts does measure 1 watt @ 8ohms and gives you a sensitivity rating for an 8 ohm speaker, but to measure a 4ohm speakers sensitivity, we still put in 1 watt, yes lower voltage, but 1 watt of power to get the output or sensitivity rating.
Where as efficiency ratings are measured strictly in voltage. We have found many variations when measuring a speakers efficiency at different frequencies that do not necessarily coinside directly with its sensitivity rating. Crossover components, cabinet designs and direct driver designs measure slightly different at different frequencies, thus being more efficient at a given frequency, yet overall might measure the same as a different speaker in sensitivity. Again, I believe that we are on the same page and I hope that I am only clarifying your statement. Any way you look at it, sensitivity vs efficiency is similar and can be confusing. Overall, just get enough power and if you are using tubes, try to find your speakers impedence phase angles and you will come out successful. Tim |
Hi Atmasphere,
I think I got it right Power = Sensitivity, Voltage = Efficiency. In the long run, it doesn't matter for what we all do and in fact the two terms are 95% interchangable. We all know what we mean when we say a speakers Sensitivity or Efficiency is 90db.
An interesting example for everyone would be what a room does to efficiency. We put set up a 90db speaker in the golden triangle in the middle of a big room, if you get a flat response, they are 90db at all frequencies. Move them back a bit and the bass is reinforced, by ??? 1 to 6 db. We still have a 90db speaker, but we just made the bass frequencies more efficient. The speaker is still a 90db sensitivity speaker, but the room just made the bass more efficient. That is the easiest example of efficiency vs sensitivity for everyone that I can think of . For Altbrewer, I have no idea how all of this will help you shop speakers, please let us know what you end up with. The best of luck, Tim |
I emailed my friend that owned SpeakerCraft/Marcof Electronics, he has designed a ton of raw drivers for several different people. As an off shoot of this discussion we were discussing how we have chosen an 8 or 15 inch driver for the same design even though an 8 inch and a 15 inch woofer both have the same sensitivity and can be designed as a woofer with the same mid and tweeter, the 15 is still more efficient because how it moved more air more efficiently. Here is his reply:
Tim, while vc resistance is used as a part of motor force calculation, so is the driver cone area. You can build what you want many many ways, but to tie efficiency directly to voice coil resistance is flaky science to say the least.
Design with the highest flux density in the voice coil gap and the highest ampere turns also in the gap with the lightest moving mass with the largest cone size will win the DB/Watt/1 meter race. It doesn't mean a darn thing about how it will sound. :)
Hope this helps some! As you already know, speaker design, is a giant pile of trade offs (at best).
Ed
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Thanks Al, I had quoted my buddy Ed above, he had told me pretty much the same as you, saying no one on the forum has argued this in absolute terms and it really doesn't matter in the context that you are using it and overall would do nothing to further anyone. So as you can see, he just laid out how it is created in a conventional driver. Good Listening, Tim |
